The present invention relates to an apparatus for pneumatically conveying bulk material.
An apparatus of this kind may include a conveyor line consisting of a plurality of conveyor line sections joined to each other via flanges and each including a rigid outer pipe and an elastic inner pipe which in pressureless state has an outer diameter which is smaller than the inner diameter of the metallic pipe and is outwardly folded at both its ends about the respective end faces of the outer pipe. Cooperating with the conveyor line is a secondary line which contains clean gas and is subdivided in sections by shut off valves responsive to a pressure difference between the secondary line and the conveyor line. Each section is connected with the interior of the conveyor line via overflow valves.
Such an apparatus is known from the German publication DE-OS 34 37 560 and operates in a manner as known from the German Pat. No. DE-PS 25 50 164 which uses the pressure difference encountered during compaction or clogging of bulk material between the conveyor line and the secondary line for introducing clean gas from the secondary line into the conveyor line along the area of the compaction of bulk material so as to dissolve the latter. In this manner, a high-speed conveying as well as the usually preferred slow-speed conveying even of such bulk material which is difficult to handle like e.g. fatty bulk material is possible without being deposited on the inner wall surface of the conveyor line and encountering a gradual closing of the latter, or formation of thick deposits at the wall surface which would cause clogging when flaking off.
Each conveyor line section in this known apparatus is provided with either a shut off valve or an overflow valve. The flanged connection between two conveyor line sections includes a centering ring, two tension rings and two flange rings which are bolted together. The end faces of the metallic pipes must be provided with welded-on rings about which the respective elastic inner pipe is folded. The manufacture is thus complicated especially since only the straight conveyor line sections are mass-producable as subsequent adjustments to the local conditions are not possible. Each apparatus must thus be individually planned and in particular when considering the multitude of existing arcs in the line path must be individually manufactured for the most part.